In many processes of producing polymers or petrochemicals, a stripping process has been operated as a process following polymerization. The stripping process uses a method such as steam stripping and distillation in order to recover unreacted monomers and solvents after reaction and reuse them. A description of the steam stripping for recovering solvents in this method is well described in Korean Laid-Open Patent Publication No. 2004-0042561. In a general steam stripping method, the polymer solution is introduced into a high-temperature water and the solvent is volatilized and removed together with water vapor using steam to recover the polymer.
The stripping unit used for stripping is for evaporating and separating mixed materials of two or more components present in a feedstock by the boiling point difference. At the upper part of a distillation system, a low-boiling material (high volatile component) is evaporated and separated in a form of the upper vapor and at the lower part of the distillation system, a high-boiling material (low volatile component) is separated in a form of condensate. The low-boiling material and the high-boiling material may also be each a single component or a mixture of two or more components.
As a representative process for separating a mixture of a polymer and a solvent, and the like using such a stripping unit, there is a synthetic rubber production process. The synthetic rubber refers to a polymer material having the same or similar physical properties as natural rubber, and includes butadiene rubber, acrylonitrile butadiene rubber, styrene butadiene rubber, solution styrene butadiene rubber or ultra high-cis polybutadiene rubber, and the like. The solvent may include (normal)hexane.
The attached FIG. 1 is a schematic diagram illustrating a solvent separation apparatus used in a general stripping process. As shown in FIG. 1, typically, in the conventional stripping process, water supplied from the water tank (10) and steam are mixed with a mixture of polymerized polymer and a solvent and supplied to the stripping unit (20). The top stream (201) discharged from the top region of the stripping unit (20) is condensed in the condenser (30) and then introduced into an oily water separator (50) through a cooler (40). The solvent separation apparatus uses a middle pressure steam (MP) as a heat source, and in this process, a large amount of energy is consumed.
Therefore, in order to reduce the energy consumed in the solvent separation process, there is a need for a method capable of recovering and using the discarded waste heat.